We will continue to explore temperature regulation of hibernating hamsters, ground squirrels and dormice exposed to freezing cold while monitoring oxygen consumption, heart and respiratory rate, and body temperature. Using discrete brain lesion and chronic electrical recording we will attempt to locate the areas of the brain which are involved in the response of hibernating animals to potentially lethal ambient cold. By serial transections of the brain or by cryogenic block with small metal thermodes we will attempt to determine what level of the CNS is influencing the sensitivity to peripheral stimuli in the hibernating animal.